复选框checkbox的JS操作

html代码：

<td width="80%" colspan="3">
<input onchange="fzChange()" type="checkbox"  name="fzunid" value="J167f5a11ea945fa99caf2e1b38dcf7e" alt="默认分组" showName="默认分组" checked='checked' >默认分组 &nbsp;&nbsp;
<input onchange="fzChange()" type="checkbox"  name="fzunid" value="Je4b830e5ded420a89834fb1dc132875" alt="朋友" showName="朋友"  >朋友 &nbsp;&nbsp;	
<input onchange="fzChange()" type="checkbox"  name="fzunid" value="J4724d6011204a1ba3d524bfd7534456" alt="同事" showName="同事"  >同事 &nbsp;&nbsp;
</td>

<input type="hidden" id="fzname"  name="fzname" value="" />

 

JS代码：

function fzChange()
{
	var obj=document.getElementsByName("fzunid");
    var theValue="";
    for(var i=0;i < obj.length;i++)
    {
      if(obj[i].checked)
      {
         if(theValue=="")
         {
        	 theValue=obj[i].alt;
         }
         else
         {
        	 theValue=theValue+"，"+obj[i].alt;
         }
      }
    }
    //alert(theValue);
    document.getElementById("fzname").value = theValue;
}